Device and method for electrolytically treating an at least superficially electrically conducting work piece

ABSTRACT

A problem during electrolytic treatment of printed circuit boards having a very thin basic metallization is that the treatment yields irregular results in various regions on the surface of the printed circuit board. In overcoming this problem the invention provides a device for electrolytically treating an at least superficially electrically conducting work piece having at least two substantially opposing side edges. The device comprises current supply devices for the work piece, said current supply devices each comprising contact strips located on the opposing side edges which are capable of electrically contacting the work piece at the substantially opposing side edges.

The invention relates to a device and to a method for electrolyticallytreating an at least superficially electrically conducting work piece.Electrolytic treatment comprises above all the process ofelectrolytically metal plating and etching thin electrically conductinglayers on printed circuit board material. The invention is morespecifically suited for use in horizontal and vertical plating lines.

The increasingly smaller structures in the printed circuit and SmardCardtechnique require ever thinner base layers to be processed. Formerly,said base layers were obtained by what is termed copper cladding whichconsisted in adhesively coupling a very thin electrolytic copper foil of15-35 μm thick to the electrically non-conducting substrate made of aplastic material. In fine line printed circuit boards, these base layersare nowadays generally obtained by electroless (chemical) metaldeposition. Such a base layer is through-plated for example and a fineline patterning with 50 μm lines and spaces is electrolyticallydeposited thereon. In order to complete the printed circuit board, areinforced base layer must be removed by chemical etching from betweenthe electrolytically metal plated circuit traces. In order for thecircuit traces not to be undercut during this etching step, the baselayer must be thin. In the fine line printed circuit technique, the baselayers used are 2-5 μm thick. In SBU (sequential build up) applications,the base layers utilized are for example made of electroless depositedcopper of but 0.3-1.0 μm thick.

The deposition of thin metal layers, more specifically copper layers,onto the printed circuit board base material, is compatible with currentprinted circuit board processing lines. Such lines are described in U.S.Pat. No. 4,776,939 and in DE 41 32 418 C1 for example. Both documentsshow lines in which the printed circuit board material is conveyorizedthrough the line in a horizontal direction of transport. In both cases,the material is conducted in a horizontal plane of transport. U.S. Pat.No. 4,776,939 describes a conveyorized line for printed circuit boardsthat has laterally arranged clamps for placing the work pieces inelectrical contact. DE 41 32 418 C1 discloses a conveyorized line havingcontacting wheels for laterally placing the printed circuit boards incontact.

It has been found out that, with metal plating being performed at arelatively high current density of for example 10 A/dm², it is no longerreadily possible to electrolytically metal plate printed circuit boardmaterial with a very thin base layer of for example 5 μm thick. In thisevent, it may happen that less or no metal at all be deposited ontoregions that are located at a relatively great distance, e.g., 50 cm,from the electrical contacting sites. Electric current is suppliedthrough the electrical contacting sites to the base layer (basicmetallization) by means of the clamps according to U.S. Pat. No.4,776,939 or of the contacting rolls according to DE 41 32 418 C1.

The above mentioned problem can be mitigated by reducing the currentdensity for example. This solution however suffers from the disadvantagethat the efficiency and the rentability of the electrolytic metalplating line are reduced as a result thereof. For, under thesecircumstances and in order to deposit a metal layer with a given layerthickness, the processing lines must be of a sufficient length to holdthe printed circuit board material for the time necessary for metalplating. This involves expenses for investment and incidentals as wellas for manpower, upkeep, maintenance and repair that make such a lineuneconomical to operate.

Using a lower cathodic current density, another disadvantage has beenfound out, which is that a thin base layer of copper that is to be metalplated dissolves in part or in whole in the usually used sulphuric acidcopper bath utilized for electrolytic metallization, so that only theelectrically non-conducting base material remains.

Further, to minimize scrap, the printed circuit board industry has beeninterested for a long time in being capable of recognizing in-time,during each electroplating procedure and for every printed circuitboard, possible thickness differences using measurements such as chargemeasurement (in ampere-hours).

One reason for differences in the coating thickness may for example befaults in establishing electrical contact due to damaged or contaminatedelectrical contacts or to a damaged feed cable.

Such type differences may also be due to changes in the electricconductivity of the electrolyte fluid as a result of the bath havingbeen altered in composition, for example with one substance beingoverdosed on one site of the bath (in the event of a failure of themixing device for example), or of different temperatures prevailingwithin the bath. These problems in performing the method not only affectthe coating thickness but also lead to a varying quality of the layerdeposited on the printed circuit board.

DE 100 43 815 A1 describes a method and a device for placing a workpiece to be processed in electrical contact in electrolytic lines. Thedevice more specifically serves to treat electrical printed circuitboards. It consists of a conveying system, a pumping system forcirculating the electrolytic bath and facilities for regenerating theelectrolyte, a plating current source for supplying the electrolyticcell, electric elements for transmitting the current from the platingcurrent source to the work piece and strip contacts that are disposedtransversely to the direction of transport of the work piece with theircontacting side turned toward the surface of the work piece that is tobe treated, further of lifting facilities for the strip contacts forcontinuous, almost vertical approach, position of rest withelectrochemical treatment of the work piece and removal of the stripcontacts from the surface of the work piece, further of a conveyingsystem for conveying the work piece through the electrolytic cell insuch a manner that the strip contacts and the work piece are preventedfrom moving relative to one another during electrolytic treatment andfinally of a switching equipment for coordinated switching of thelifting facilities for the strip contacts and the conveying systems forthe work piece. In accordance with the invention, the device is utilizedas follows: the work piece is conveyed into the electrolytic bath whereit is contacted with the electrolyte. The electrically conductingsurfaces are placed in electric contact and are conductively connectedto the plating current source. For electric contact, the strip contactsare placed onto the surface of the work piece against which they arepressed. The work piece is conveyed through the electrolytic cell formedby the electrodes and the work piece in such a manner that, from themoment the strip contacts have been positioned at the latest, said stripcontacts and the work piece are prevented from moving relative to oneanother. The work piece is electrochemically treated while the stripcontacts are placed on the surface thereof. After the processing step iscompleted, the strip contacts are lifted from the surface of the workpiece. As the strip contacts are being lifted, the work piece is movedrelative to the strip contacts and the electrodes of the electrolyticcell, this motion being due to transport. This sequence, fromelectrolytically contacting the surfaces with the strip contacts to thelast mentioned method step, is continuously repeated.

DE 100 43 817 A1 suggests a method and an arrangement for a work piece,more specifically a printed circuit board, that is to be treatedelectrochemically. The arrangement comprises a working tank for holdingthe electrolyte and the work piece, a fluid delivery facility for theelectrolyte for circulating the electrolyte through the working tank,electrolyte filters and electrolyte conditioning tanks, an equipment forconveying the work piece out of the working tank, a contact electrode inthe working tank that consists of an electric contact strip and of acounter electrode disposed in immediate proximity thereto, anelectrically insulating means that is disposed between each contactstrip and each counter electrode for forming small electrolytic cells, aplating current source and the associated electric conductors forsupplying current to the small electrolytic cells. In accordance withthe invention, the arrangement further comprises a contact electrodewhich conforms to the shape of the work piece, a conveying member in theworking tank that is designed and controlled in such a manner that, aslong as the contact electrode is resting on the surface of the workpiece, the contact electrode and the surface of the work piece areprevented from moving relative to one another due to transport, acontrol facility for synchronizing the advancing of the work piece or ofthe contact electrode in the working tank with the opening and closingmovements of the contact electrode as well as a moving member forcyclically performing the following method steps: causing the contactelectrode and the work piece to get nearer to each other, placing thecontact strips onto the surface of the work piece, allowing the contactstrips to rest on the surface for electrolytic treatment, lifting thecontact strips from the surface and mutually removing the contactelectrode and the work piece and repositioning the work piece relativeto the contact electrode.

The object of the present invention now is to find a solution permittingto avoid the drawbacks of the known devices and methods. The device andthe method to be found are more specifically intended to make itpossible to assess the quality of metal deposits during themanufacturing of printed circuit boards and to remedy quality relatedproblems upon detection thereof. Economical operation is further to beachieved by which a metal coating can be deposited with uniformthickness onto large-format work pieces, more specifically ontoelectrical printed circuit boards and other circuit carriers, without anexisting thin basic metallization interfering therewith. The device andthe method in accordance with the invention are also intended to allowfor other electrolytic treatments that are also to be uniform onlarge-format work pieces such as an electrolytic etching process forexample. The sensitive useful zone of the printed circuit boards is notallowed to come into contact with the contacts.

This object is achieved by the device described in claim 1 and by themethod described in claim 26. Special implementations of the inventionare described in the subordinate claims.

The superficially electrically conducting work piece referred tohereinafter is to be construed as either any work piece that is made inits entirety of electrically conducting material, for example of ametallic material, or as any work piece that is electrically conductingon its surface only, for example by providing it with a metallic surfacelayer.

By electrical printed circuit boards circuit carriers are meant whichare made from a board-shaped laminate that may be built up in aplurality of dielectric and metallic layers and may comprise vias(through-hole vias, buried vias and blind vias). The term may also beconstrued, i.a., as any structure that does not have the shape of aboard and serves to electrically connect electric components which areattached and placed into electric contact on these circuit carriers.They may for example refer to three-dimensional structures which carrycircuit trace structures. Moreover, by electrical printed circuitboards, other circuit carriers are also meant such as for example chipcarriers including hybride systems. In principle, the term work piece isnot to be construed as an electrical printed circuit board only, but asany product serving other purposes as well.

When hereinafter the work piece is said to be disposed opposite thecounter electrodes, it is meant that the counter electrodes and the workpiece are held a determined distance apart from each other, preferablyin parallel planes in which are located the counter electrodes and thework piece if said counter electrodes and said work piece are shapedlike a board. In other cases, in which the counter electrodes and thework piece have a complex three-dimensional structure, an arrangement isto be construed in which the counter electrodes and the work piece areheld a pre-determined distance apart, certain surfaces of the counterelectrodes and of the work piece being turned toward each other andbeing held a mean distance apart from each other.

When hereinafter two substantially opposing side edges are said to beprovided, it is meant that the side edges are held apart to the greatestpossible distance. As viewed from the one side edge, the other side edgeis located on the other side of an imaginary centre of gravity of thework piece. In the case of substantially opposing side edges ofboard-shaped rectangular work pieces for example, the side edges areparallel. In this case, there are two pairs of opposing side edges.

The term contact strips is to be construed herein after as any electriccontacting element intended to supply current to the work piece thatcomprises elongated contact areas for transmitting the current to thework piece or that comprises a plurality of small single contacts whichare closely spaced, for example less than 1 cm apart, and are embeddedin elongated current supply devices. The very single contacts can alsobe configured to be elongated, preferably being disposed in a row, andcan be carried by springs for enhanced fit on the metal surfaces. As aresult, the contact strips have a length/width ratio of the electriccontact area that is substantially greater than 1. This ratio may forexample be at least 5, preferably at least 10 and most preferably atleast 20. The upper limit of this ratio is given by the length of theside edges and a minimum width of the contact areas, which in turn isdetermined by the suitability of the contact area for transmitting tothe work piece the greatest possible current.

When current supply devices, contact strips, supporting frames,supporting frame legs, contacting frames, supporting points in atreatment tank, supporting elements, counter electrodes, frame covers,processing fluid feed and drain lines in frame covers, treatment tanks,entry and exit areas, conveying devices, current supplies and processingstations are referred to herein after, these terms are each to beconstrued as one or several of these elements.

The invention serves for electrolytically treating an at leastsuperficially conducting work piece, more specifically an electricalprinted circuit board. By electrolytic treatment of the electricalprinted circuit boards it is meant that they may be electrolyticallymetal plated or electrolytically etched or electrolytically treated inany other way (for example by electrolytic oxidation or reduction). Theinvention is more specifically related to manufacturing electricalprinted circuit boards that are treated either in dip tanks in which theelectrical printed circuit boards are immersed in the processing fluidin a substantially vertical orientation for electrolytic treatment or inwhat are termed conveyorized lines in which the electrical printedcircuit boards are conveyed in a horizontal direction of transport andare contacted with the processing fluid and treated electrolytically inthe process. In the latter case, the electrical printed circuit boardsmay be held and conveyed in a horizontal or vertical orientation. In apreferred application of the present invention, electrical printedcircuit boards are manufactured starting from an electricallynon-conducting material the outer faces of which are at first providedwith a very thin basic metallization only. Said very thin basicmetallization is reinforced in accordance with the invention by means ofelectrolytic deposition.

The device according to the invention comprises current supply devicesfor the work piece. The current supply devices in turn each comprisecontact strips provided on the substantially opposing side edges of thework piece. Therefore at least two contact strips may be provided at theopposing side edges. The work piece is placed in electric contact with acurrent source through said current supply devices.

The customary, relatively insecure current transfer from the directcurrent source via cables to a flight bar reception, from there tomovable flight bars, and then through racks or clamps to the work piecein vertical electroplating lines is substantially simplified as a resultthereof.

As contrasted with the present invention, the electrolytic treatment ofvery thin base layers on an electrically insulating material is notsatisfactory using the known devices and methods:

Thin base layers, for example 0.3 μm thick electroless deposited copperlayers, have relatively high electrical resistance. Said resistance isup to 100 times higher than that of the hereto before customary 17.5 μmthick base layers made from electrolyte copper. Said difference is i.a.due to the fact that the resistance of electroless deposited copperlayers is higher than that of electrolytically deposited copper.

The current in an electrolytic cell is distributed through the baselayer and is run to the contacting means that electrically connects thework piece, a printed circuit board for example, to the plating currentsource.

If the contacting means of an electrolytic metal plating line contact aboard-shaped work piece at one edge only, the entire current must flowto the opposing edge through the thin base layer. At the beginning of anelectrolytic treatment, when the base layer is still thin, said currentcauses the voltage to drop considerably in the base layer. Due to themetal plating said voltage drop reduces the cell voltage at varioussites on the surface of the work piece relative to a counter electrodeto different extents. During electrolytic metal plating, the base layerthickens with increasing treatment time, with the electric conductivityincreasing as a result thereof. During electrolytic etching, theelectric conductivity is reduced accordingly. As a result, theelectrolytic treatment of the surfaces is non-uniform in both cases,which is undesirable. Using conventional plating lines due to thediffering thickness in base metallization the electrolytic treatmentvaries from one product to the other. However, in conveyorized platinglines usually provided with a plurality of anodes, it is required totreat various different types of work pieces the base layers of whichhave very different thicknesses in a thickness ratio range of up to1:100 without differences in quality.

The problem described could be overcome in using for example one of thedevices according to DE 100 43 815 A1 and DE 100 43 817 A1, since thespacing between the contacting sites can be minimized. However, thisapproach suffers from the disadvantage that during treatment noelectrolytic treatment is allowed to take place beneath the contactstrip because the antipole (anode or cathode respectively) is completelyshielded. This results in non-uniform electrolytic treatment. Thisdisadvantage is intended to be avoided by conveying the work pieces incycles in many small stages and by delaying the positioning of thecontact strips on ever different sites of a printed circuit boardrelative to the advance of the work. However, this method suffers fromthe disadvantage that the frequent repositioning of the contact stripswithout applying electric current is very time-consuming with theprinted circuit boards not being electrolytically metal plated duringthis period of time. As a result, the line must be lengthened, whichinvolves higher manufacturing costs. Moreover, the contacts are alwayspressed against the useful area of the printed circuit boards. Forexample undesired metal deposits, dirt particles or chips on thecontacts may get pressed into the initially still thin and thereforesensitive base layer, resulting in scrap. Furthermore, these approachesdo not allow measurements that permit to detect possible coatingthickness differences to be carried out individually for every singleprinted circuit board.

By contrast, it has been found out that the device in accordance withthe invention, which is provided with contact strips for placing thework piece in electric contact, said contact strips contacting the workpiece on opposing side edges thereof for establishing an electriccontact there, is perfectly suited to solve the problems that ariseusing the known devices and performing the known methods, morespecifically if, while contacting work pieces with a preferablyrectangular shape, the contact strips extend over substantially theentire length or at least over a substantial portion of said length, forexample over at least 75% of the length of the side edges:

Uniform electrolytic treatment is achieved in placing the opposing sideedges of a work piece in electric contact with a very thin metallic baselayer. Under these conditions, a voltage drop due to increasedelectrical resistance of the base layer has not the same negative effectthan with customarily contacted work pieces.

Moreover, in this way of contacting the work, there is much lesselectrical transition resistance. The direct current source and the workpiece can be connected through a continuous cable leading from theconnection terminals on the rectifiers to the contacting frame. Fromthere electric current is directly conducted to the site contacting thework piece. Relying on moving flight bars for transmitting the currentto the work piece results in substantially more insecure sites withtransition resistance.

In a preferred embodiment of the invention, the contact strips areimplemented in such a manner that they are capable of holding the workpiece. A preferred structural design is thus achieved: Since the contactstrips are capable of holding the work piece, no further holding meansare required. As the contact strips serve to transmit electric currentto the work pieces, they must be pressed firmly against the surface ofthe work piece in order to establish good electrical contact permittingto supply even high currents. Since a relatively great force is neededtherefore, it is advantageous to concurrently use this force to hold thework piece.

To effectively realize the functions of the contact strips ofestablishing electrical contact and of holding the work pieces, at leasttwo respective contact strips are joined together in one contactingframe in a preferred development of the invention. In anotherembodiment, two such contacting frames are linked together, especiallypivoted to one another, preferably in a longitudinal axis, and morespecifically for closing, so that the work piece can be removablyclamped between the contacting frames. Contact strips, forming threerespective sides of a rectangle and being pivoted together viarespective longitudinal axis at their longitudinal edges, may forexample form a three-sided frame for the work piece, with the contactstrips disposed on one side of the work piece being either joinedtogether or connected to the treatment tank through holding members andthe contact strips located on the other side of the work piece beingconnected to the other contact strips through the longitudinal axesonly. A fourth pair of contact strips can be provided on the fourth sideof the rectangle with the one of this pair of contact strips beingconnected to the other contact strips on the same side of the work pieceor to the treatment tank through holding members. The other one of thispair is linked to the first one of this pair. To permit introduction ofthe work piece from the top into the vertically standing arrangement ofcontact strips, the hinge-linked fourth contact strip must be able to bedeflected at least 180 degrees relative to the plane in which the workpiece is being held. If level work pieces are lowered from the top intoa treatment tank, the pivotable contact strips are opened. After thework piece has been lowered, said contact strips are folded against thework piece which they clampingly hold between them. The contactingframes can be attached to supporting frames. As a result, the work piececan be taken hold of by contacting frames and be concurrently fed withelectric current for electrolytic treatment. Manipulation of the workpiece is thus substantially facilitated.

A major advantage of the present invention is that it permits toquantitatively determine, during the electrolytic treatment already,whether the treatment is conducted in compliance with the givenstandards. Quality parameters are defined for this purpose and aredetermined individually for each work piece. Such individual measurementat each work piece is possible since the work pieces are is electricalcontact with the contact strips and since a work piece has no directelectrical connection to neighbouring work pieces, as for examplethrough the electrically conducting flight bar. Therefore appropriateprocess parameters can be controlled by the selective online measurementof current, voltage, charge (ampere-hours) and potentials much moreaccurately than with the known devices. Further, for example the flowrate of processing fluid on certain sites of the work piece and thebrightness of the metal deposited can be determined individually forevery single work piece.

The quantity of the metal deposited during the electrolyticmetallization of printed circuit boards can be measured for each printedcircuit board individually for example. For this purpose, measuringprobes in particular can be disposed at a site located proximate thesurface of (opposite) the printed circuit board. These measuring probespermit to measure for example the electrical resistance between thesurface of the printed circuit board and the measuring probe both beforethe electrolysis current is switched on and after it has been switchedoff in order to determine the coating thickness of the metal. A counterelectrode (an anode in metal plating) can be employed as a measuringprobe if it is spatially associated with the printed circuit board. Theelectrical resistance may also be measured between discrete contactstrips, for example between two opposing contact strips, and be used fordetermining the coating thickness of the metal. The electricalresistance being measured between the contact strips can also bedetermined before contacting the printed circuit board with theprocessing fluid.

Deviations from reference values can be determined quickly by measuringthe electrical resistances and an alarm may be triggered for example.For this purpose, reference values are taken as a basis for every singletype of printed circuit board and the differences between the actuallymeasured values and the respective reference values are determined foreach printed circuit board.

The amount of metal deposited can be determined with even more accuracywith the help of the known surface of one single printed circuit boardthat comes into effect in the electrolytic treatment and of a current(charge) measurement during the electrolysis treatment (ampere-hourmetering of the consumed current). For this purpose, the current thatflows to every single printed circuit board is measured separately andpossibly integrated on the electrolysis time (determined quantity ofcharge which is proportional to the deposited or dissolved amount ofmetal, respectively). Furthermore, the current flowing to a counterelectrode (during metallization of an anode) can also be determinedindividually. The current or the amount of current integrated on timewill suffice to determine whether the counter electrode and thecontacting process operate without failure. Passive areas, which preventelectrolytic reactions from taking place, could for example have formedon the counter electrode. This would be immediately detected by thecurrent or charge measurement. If the counter electrode would not beassociated to an individual printed circuit board with regard to spaceand current supply as in the case of a conventional arrangement ofprinted circuit boards in a plating tank, this measurement is butinsufficiently indicative of the efficiency of the counter electrode.If, by contrast, the counter electrode is also associated with regard tospace and current supply to this individual printed circuit board, suchtype measurements are directly indicative of the actual electrolysisconditions for this printed circuit board.

An alarm can be triggered in the event the electrolysis current forexample deviates from the reference value and manual or automaticprovisions can be made for compensating for possible failure duringelectrolytic treatment. The metal deposition time can be extended or thecurrent density increased for example. In vertical conveyorized platinglines, conveyor carriages for moving printed circuit boards from oneprocessing station to the other are used. As these carriages are freelymovable above the path of travel of the printed circuit boards and areequipped with grabbers for every single printed circuit board,additionally provided treatment devices may be approached by the printedcircuit boards to be repaired in the event deviations from the referencevalue of for example the coating thickness on individual printed circuitboards are measured in order to compensate for deviations detected bycontrol measurements. If, due to damage, an increased transitionresistance is for example noticed on a certain contact strip contactinga printed circuit board, the printed circuit board of concern can besubjected to a post-treatment in a special processing station in whichevery single one of the contact strips can be supplied with individualcurrent and voltage values. Accordingly, in this case, the printedcircuit board is supplied with current through only that contact stripat which failure occurred.

Other physical parameters of the work piece can further be determinedfor each individual piece. The brightness of the metal deposited may forexample be measured. If deviations from a reference value are detected,a printed circuit board is for example subsequently treated in anotherbath having a special electrolyte composition. If the printed circuitboard is treated in a vertical conveyorized line, the printed circuitboard can be transferred automatically, through a suited control systemfor the transportation thereof, to a repair station where the fault isrepaired. A special control programme for repairing the fault may be runfor the purpose. Such a programme may for example also include thatexcess metal deposited onto the printed circuit board is removed againby reversing the polarity of the plating current at the printed circuitboard of concern. Further, metal can be removed from a printed circuitboard by shielding a supporting frame carrying the contact strips whileanother printed circuit board is being metal plated concurrently.

All of the aforementioned measurements can be acquired and recordedusing a connected computer system. Faults may thus be inferred therefrom at a later stage as well, permitting selective correcting measuresto be taken.

The contact strips may more specifically be fastened to supportingframes. This permits the device to be simple in construction if thecontact strips are not joined together to form a contacting frame.

In a preferred embodiment of the invention, the supporting frames havesubstantially the same size as the work pieces. Moreover, the supportingframes may also have substantially the same shape as the work pieces.With the supporting frames being configured to have such a shape andsize, they are capable of grasping the work pieces, for exampleelectrical printed circuit boards, individually and of holding themduring electrolytic treatment. Accordingly, the supporting frames mayfor example have four supporting frame legs which are orientedsubstantially parallel to the side edges of the work piece if the workpiece is board-shaped and rectangular, the supporting frame legs beingattached to the contact strips. With this implementation and arrangementof the supporting frames and contact strips, for electrolytic treatmentelectric current may be fed to the work piece, more specifically aprinted circuit board, via the contact strips. As the supporting framesand the contact strips are substantially conformed to the shape and sizeof the work piece, automated manipulation of the work piece is possible.As a result, the work piece can be placed in electric contact with thecurrent source and mechanically retained in a simple and reliable mannerwith the advantages in accordance with the invention, i.e.,non-problematic current supply with even very thin metallic base layers,being achieved. Further, the useful area remains untouched duringtreatment as opposed to the devices and methods disclosed in DE 100 43815 A1 and DE 100 43 817 A1.

Further, alternatively or additionally, at least two contact strips maybe joined together in one contacting frame and two contacting framesand/or supporting frames can be linked together through a respective oneof the contact strips, preferably pivoted through an axle/hinge, so thatthe rectangular board may be removably clamped between the frames.

A simplified automated grasping and electrically contacting of theboard-shaped work pieces is achieved in particular if at least twosupporting frames are provided, with said supporting frames beingassociated to a respective one of the sides of the work piece. In thiscase, the supporting frames, which are preferably connected by an axle,may be configured to be foldable into an open and closed condition likea cassette in order to receive the board-shaped work piece. In thisevent, the contact strips are located between the covers of thecassette. The cassette is folded open to receive the work piece. Oncethe work piece has been inserted between the cassette halves by means ofa conventional horizontal or vertical conveying facility, said cassettehalves are folded together so that the work piece is clamped thereinbetween and is thereby placed in electric contact with the currentsource.

In another implementation, the work piece can be directly held andremovably clamped by the supporting frames for electrolytic treatment,meaning that the supporting frames are then directly adjacent thesurface in the region of the edges (of cut) of the work piece. Inanother embodiment, for electrolytic treatment the work piece can alsobe held and removably clamped by the supporting frames via the contactstrips. In this case the inventors have taken advantage of the fact thatit is necessary, in order to achieve efficient current transfer from thecontact strips to the work piece, to provide a minimum closing forcebetween the contact strips and the work piece. This force may of coursealso be used to hold the work piece. In the case of the embodiment ofconcern, the supporting frames exert the force on either side (front andback side) of the work piece via the contact strips. Accordingly, thelatter embodiment offers advantages over the previous one. The workpiece in this case, too, may likewise preferably be clamped by its edgein order to prevent touching the area on the surface of the work pieceto be treated. A combination of the afore mentioned embodiments is ofcourse also possible, meaning that the work piece may also be held andremovably clamped by both the supporting frames and the contact strips,for example in the event the work piece is to be electrolyticallytreated on one side only so that contact strips are only provided onthis side of the work piece.

The work piece is preferably received in, and held by, the supportingframes and/or the contacting frames. Next, electrolytic treatment isstarted by supplying electric current to the work piece through thecurrent supply devices, preferably through the contact strips. Uponcompletion of the electrolytic treatment, electric current supply isdisrupted and the work piece is released from the supporting framesand/or contacting frames (contact strips) and advanced by the conveyingfacilities.

To secure the supporting frames in a treatment tank, the supportingframes may be supported through supporting elements on supporting pointsin the tank. The supporting elements are preferably configured to bemovable so that the position of the supporting frames relative to thesupporting points in the tank may be varied. As a result, the supportingframes may be adjusted together with the work piece within a treatmenttank. This embodiment offers major advantages over conventional devicesfor electrolytic treatment:

If counter electrodes, such as anodes for electrolytic metal plating,are for example stationarily disposed in the treatment tank, thesupporting frames holding the work piece can be individually orientedrelative to the position of the counter electrodes. Further, ifmeasuring facilities, such as measuring probes disposed in proximity tothe surface of the work piece, are provided to determine the effect ofthe electrolytic treatment onto the respective work piece, the positionand orientation of the work piece retained within the treatment tank bythe supporting frames can be optimized relative to the counterelectrodes in order to achieve a very uniform electrolytic treatment.Such an optimization is made possible by moving the supporting elements,with such supporting elements being for example provided on a respectiveone of the corners on either side of a rectangular cassette consistingof two supporting frames for holding the work piece. The supportingelements are supported on opposing sides of the cassette by supportingpoints located on the walls of the tank for example, with eight of suchsupporting elements being moved in such a manner that the spacingsbetween the work piece and the counter electrodes are optimized withregard to the uniformity of the electrolytic effect on the work piece.Under normal condition uniformity will be achieved if the distancesbetween the counter electrodes and the surfaces of the work piece areidentical.

If more specifically board-shaped work pieces, such as an electricalprinted circuit board, are treated, the supporting elements may beconfigured in such a manner that the printed circuit board is clampedbetween two supporting frames and/or contacting frames that areassociated to a respective one of the sides of the printed circuit boardafter said circuit board has been conveyed to the frames by means ofconveying facilities: The circuit board is prepared to be received inthe cassette formed by the supporting frames by being conveyed betweensaid frames. The frames are held apart for this purpose. The respectiveframes may for example be pivoted to one another through a common frameleg so that the cassette needs only be folded together to take hold ofthe circuit board. As the cassette is being folded together, theopposing side edges of the circuit board are brought into electriccontact with the current source.

As a matter of course, the electrolytic treatment device also comprisescounter electrodes that are disposed opposite the work piece. In aparticularly preferred embodiment, the counter electrodes are mounted tothe supporting frames. This arrangement is also taken advantage of toreadily adjust the counter electrodes relative to the work piece. Toprovide optimum treatment for the work piece, the work piece needs to beaccurately aligned relative to the counter electrodes. This may beachieved in particular by aligning each work piece individually, this inturn being achieved if the counter electrodes and the work piece aredisposed in one common cassette that is formed by the supporting framesand/or the contacting frames.

In another improvement of the invention, the counter electrodes aredisposed substantially parallel to the work piece and are movablycarried on the supporting frames to which they are mounted. The counterelectrodes are preferably mounted in such a manner that they areslidable parallel to the surface of the work piece. Inhomogeneities(irregularities) on the surface of the counter electrodes are thuscompensated during electrolytic treatment by constantly or at leastintermittently (cyclically) moving the counter electrodes parallel tothe surface of the work piece during treatment. It is advantageous tomove the counter electrodes in order to prevent them from leaving animpression in the form of differences in coating thickness on theprinted circuit board, said impression being the result of possiblyoccurring irregularities in the geometrical shape and/or of the electricconductivity of the counter electrodes. Irregularities on the counterelectrodes may for example be the result of passive sites (for examplethrough unintended wear) or of fluid passage ports (necessary voids) inthe counter electrode. Moving the counter electrodes aims at achievingthat such type voids in the counter electrodes distribute evenly forpossibly the same period of time over the surface of the printed circuitboard.

The same effect can of course be achieved by stationarily disposing thecounter electrode and by moving the work piece together with the contactstrips instead.

Even if the counter electrodes are moved parallel to the surface of thework piece during electrolytic treatment, the size of the counterelectrodes is preferably chosen so as to approximately correspond to theelectrolytically to be treated useful area on the work piece (withoutedges of cut). Since the area of the counter electrode may have about oreven exactly the same size as the useful area on the printed circuitboard, excess metal is prevented from depositing in the border regionsof the printed circuit board as a result of the concentration of theelectric field lines in the border regions. Optimum thickness uniformityof the metal deposit is achieved if the moving counter electrode areacovers the useful area of the printed circuit board just enough toprevent the surface of the counter electrode from ever directly opposingthe border regions in order to prevent electric field lines toconcentrate on these border regions. Separating membranes may also bedisposed between the counter electrodes and the work piece.

In another preferred embodiment of the invention, additional covers aredisposed on the supporting frames and/or on the contacting frames so asto form compartments that are defined by the covers and the work piece.As a result, separate processing compartments, in which definedconditions of flow on the surface of the work piece can be adjusted, canbe formed, together with the accommodated work piece, in the cassettes,which are formed by the supporting frames and/or contacting frames. Morespecifically, the flow through small holes in printed circuit boards canbe promoted by a build up of hydraulic pressure within the processingcompartment. A cover can be fluid-tight and be made from plastic boards,a tight plastic fabric or an ion-permeable membrane.

Another advantageous development of the invention consists in disposingthe covers in such a manner that the counter electrodes are disposedwithin the closed compartments. Electrolytic cells, which are associatedwith each work piece, are thus formed, said electrolytic cells beingformed by the respective surfaces of the work piece and the counterelectrodes facing them.

In order to constantly or at least intermittently supply theelectrolytic cells with fresh electrolyte fluid, feed lines for feedingthe processing fluid to the closed compartments and drain lines forcarrying the fluid off the closed compartments are provided in thecovers and/or the supporting frame.

As a result, in a preferred embodiment, the device in accordance withthe invention is configured in such a manner that the supporting frames,the contact strips and counter electrodes contained in the device aremovable together as one combined unit (cassette) in such a manner thatthe work piece can be held by this unit during electrolytic treatmentwhile the contact strips can be brought into electrical contact with thework piece, further that the work piece may be released from said unitafter the electrolytic treatment has been performed and that theelectrical contact between the contact strips and the work pieces can beagain disconnected.

Such a cassette may for example also be utilized for electrolyticallytreating work pieces in a dip plant having a plurality of treatmenttanks. Prior to immersing the work piece in a first processing fluid ina first treatment tank, the work piece is, for this purpose, allowed tobe received in, and held by, the supporting frames and/or contactingframes having contact strips by being removably clamped therein between.Next, the work piece being held by the cassette and brought intoelectric contact with the contact strips is electrically connected tothe current source through removable electric contacts at the cassetteand electrolytically treated. After treatment, the cassette is againdisconnected from the current source, lifted from the first treatmenttank and consecutively immersed into further processing fluids in othertreatment tanks and, if necessary, again electrically connected to thecurrent source and disconnected there from again. Upon completion of thetreatment in the dip plant, the work piece is released from thecassette.

More specifically, such a cassette can be part of a conveyorized platingline or of a dip plant for treating work pieces in the form ofelectrical printed circuit boards. In this case, the inventive device inthe conveyorized plating line further comprises treatment tanks that areeach equipped with entry and exit regions for the printed circuitboards, with conveying devices for the printed circuit boards and withcurrent supply conductors for the current supply devices. The cassettesholding the circuit boards are thus introduced into the device in theconveyorized line through an entry region. In the device, a printedcircuit board contained in the cassette is electrolytically treated.After the printed circuit board has been electrolytically treated, thecassette is allowed to exit the device through an exit region. Theconveyorized line can be comprised of a plurality of such devices havingentry and exit regions. The cassettes may be supplied with currentthrough conventional electrical contacting elements such as described inU.S. Pat. No. 4,776,939 and DE 41 32 418 C1 for example.

For treating the printed circuit boards in such type conveyorized lines,the work piece is first conveyed in a horizontal direction of transportto the supporting frames and/or contacting frames. There, it is receivedin, and removably clamped by, the cassette formed by said supportingframes and/or contacting frames and contact strips. Once it has beenreceived by the supporting frames and/or contacting frames, the workpiece being contained in the cassette is electrolytically treated in theconveyorized line. The counter electrodes are stationarily mounted inthe respective processing stations or installed in the cassette. Afterthe respective treatment has been performed, the work piece is releasedfrom the supporting frames and/or contacting frames so that it may beadvanced to further processing devices in the conveyorized line.

For treatment in a horizontal conveyorized line, two method variants maybe performed:

On the one hand, the cassette holding the work piece can remainstationary in the conveyorized line during the electrolytic treatment.In this case, the work piece is brought near to the opened cassette andis introduced therein. After the cassette has been closed and the workpiece removably clamped, the latter is electrolytically treated. Thecassette is not allowed to advance in the conveyorized line duringtreatment in this variant. After treatment, the cassette is opened againand the work piece is released so that it is allowed to be conveyed tothe next processing device in the conveyorized line.

In an alternative variant of the device, during electrolytic treatmentthe cassette holding the work piece is conveyed in the conveyorized linein horizontal direction of transport from an entry region to an exitregion. Once the work piece has been released, the cassette is movedback from the exit region to the entry region where it is intended toreceive a new work piece.

For an electroplating treatment having various steps in a given order,the work piece may be treated both in electrolytic baths (with electriccurrent being supplied to the work piece) and in chemical baths (withoutany electric current supply). Chemical baths do not need any currentsupply devices or counter electrodes. In this case, all of the elementsof the processing device described herein can be provided for, thecontact strips or contacting frames being replaced by other elements,e.g. holding elements, that may be configured to be folding strips orfolding frames or alternatively strips or frames which are able toremovably clamp the work piece by a parallel movement of these strips orframes.

It may further be advantageous to convey printed circuit boards from onetreatment tank to the other without the help of a flight bar. For thispurpose, a conveyor carriage for conveying the boards may be equippedwith grabbers for taking hold of every single printed circuit board. Inthe chemical treatment tanks in such a case, holding means for theprinted circuit boards must be substituted for the contacting frames(used in an electrolytic bath). These means are the aforementionedfolding strips or folding frames or alternatively strips or frames whichare able to removably clamp the work piece by a parallel movement of thestrips or frames.

The electric current source may be a direct current source or a currentsource delivering pulsed current, unipolar pulse current or bipolar(reverse) pulse current for example.

The invention is best understood when read in conjunction with theexemplary FIGS. 1 through 12.

All of the Figures are schematic and not to scale.

FIG. 1 is a cross-sectional view of a vertical dip tank having twocontact strips according to the present invention with supportingframes, as viewed from the front;

FIG. 2 a is a cross-sectional view of the details of the inventivecontact strips on the supporting frame (section B-B of FIG. 1);

FIG. 2 b is a detail of FIG. 2 a;

FIG. 3 is a cross-sectional view of the contact strips with supportingframes having an additional rear cover;

FIG. 4 is a cross-sectional view of a vertical dip tank with twoinventive contact strips similar to FIG. 1, as viewed from the front;

FIG. 5 is a cross-sectional view of a horizontal electroplating modulewith contact strips in accordance with the invention, as viewed from thefront;

FIG. 6 is a cross-sectional view of a detail of a special inventiveembodiment having double contact strips that may be opened and closedlike tongs; the viewing direction corresponds to that of FIG. 2 a;

FIG. 7 shows the double contact strips of FIG. 6 in the openedcondition;

FIG. 8 shows an arrangement of double contact strips disposed on threesides of the work piece, a printed circuit board in this case, as viewedin the direction C denoted in FIG. 6;

FIG. 9 is a cross-sectional view of another embodiment of a vertical diptank, as viewed from the front;

FIG. 10 is a preferred embodiment of a contacting frame, comprising fourcontact strips, made from a resilient flat material;

FIG. 11 is a sectional view through the contacting frame of FIG. 10taken along line A-A, as viewed in the direction denoted in FIG. 10;

FIG. 12 shows a vertical dip tank with two contacting frames that areslidable parallel to each other and with a printed circuit boarddisposed therein between.

To provide a better understanding of the invention, it is assumed hereinafter that the work piece is either a printed circuit board or a printedcircuit foil. For simplification sake, it is always assumed that thework piece is a printed circuit board. Of course, the work piece may beany piece that is chemically or electrolytically treated in accordancewith the invention.

In the following, like reference characters and numerals refer to thesame parts through the different views.

FIG. 1 is a cross-sectional representation of a vertical tank 4 forelectrolytic metal plating in vertical dip plants as viewed from thefront. The front wall is therefore removed to better show the details.

The bath tank 4 is filled with a constantly circulated electrolytefluid. The printed circuit board 1 having through-holes as well as thecontact strips 5 abutting the circuit board 1 and a flight bar 2 holdingthe circuit board 1 extend into the plane of the drawing. In principle,the contact strips 5 are not only suited for electrically contacting theprinted circuit boards 1 but also for other type of work pieces as longas the work piece 1 can be contacted in the border region thereof. Theprinted circuit board 1 blank is generally of greater dimensions thanthe finished board. For this purpose, the outer border of the circuitboard 1 is later cut off on all of the four sides. This edge of cut 24is used for example to make registration bores or to attach andelectrically contact the printed circuit board 1 in this region. Inpractice, the edge of cut 24 has a width of at least 10-12 mm. In FIGS.2 a and 2 b, the edge of cut 24 is denoted as a dashed line separatingthe edge of cut 24 from the printed circuit board 1. The printed circuitboard 1 is fastened to the flight bar 2 through a work piece holder 3.

Alternatively, the conveyor system can take hold directly of the printedcircuit board 1 by the upper edge of cut 24 thereof by means of grabbers(not shown) and move it to the processing station and withdraw it therefrom. For loading the processing station the board 1 is lowered into thebath tank 4 and then grasped and concurrently brought into electriccontact with the current source by means of the contact strips 5.Accordingly, the flight bar 2 may be totally absent.

The contact strips 5 are made from a plastic material and have a metalinsert or they are made from metal, in which case they are provided,except for the contacting regions, with an insulating coating to preventthe surface of the contact strips 5 from acting as an electric conductorand, as a result thereof, as a thief cathode. In FIG. 1 there areprovided a front and a rear contact strip 5 for treating the front andthe rear side of the printed circuit board 1, respectively. The contactstrips 5 have to exhibit relatively high stiffness to enable thespring-loaded contact elements 14, shown in detail FIG. 2 b, to beplaced in contact with uniform pressure.

The contact strips 5 are fastened within the bath tank 4 through arespective supporting frame 17 so as to be horizontally slidable (seealso FIG. 2 a). The contact strips 5 are fastened to, and supported by,the wall of the tank 4 through the supporting frames 17, throughmounting boards 27 provided on the side of the supporting frames,displacer pistons 23, displacer cylinders 22 and mounting boards 21provided on the side of the tank 4. Together with the contact strips 5,the supporting frames 17 can be displaced in a horizontal direction inthe direction of the arrows shown by actuating the displacer pistons 23inside the displacer cylinders 22 in order to receive and thereafterremovably clamp the circuit board 1. The distance of displacement of thesupporting frames 17 depends on their tendency to swing as the printedcircuit board 1 is being lowered into the bath tank 4, since generallysaid circuit board 1 cannot be fastened to the flight bar 2 or thegrabber of the conveyor carriage so as to hang in an exactly verticalposition, as well as on the thickness of the printed circuit board 1. Inpractice, a clearance of 50-100 mm between the contact strips 5 and theprinted circuit board 1 will do. To introduce the printed circuit board1 into the tank 4, the contact strips 5 are moved together by means ofthe displacer cylinders 22 and the displacer pistons 23 mounted to thesupporting frame 17 using an auxiliary energy (not shown) such ascompressed air or of a hydraulic fluid. As a result thereof, the contactstrips 5 are caused to move toward the wall of the tank 4 thus clearingthe space needed to lower the printed circuit board 1 into the bath tank4. On the side of the supporting frame 17, the displacer cylinder 22 andthe displacer piston 23 are mounted to the mounting board 27 which isattached to the supporting frame 17, on the side of the tank 4 they areattached to the mounting board 21. The supporting frame 17 with thecontact strips 5 can be displaced not only through the above mentionedauxiliary energy but also through motor driven drives such as aneccentric drive. The displacement enables the supporting frame 17 andthe contact strips 5 to be supported by the wall of the bath tank 4 andto be fixed within the tank 4 as a result thereof.

The counter electrodes 16 required for the electrolytic process arespaced a given distance apart on one or both sides of the printedcircuit board 1 and are plane-parallel relative thereto (see also FIG. 2a). This distance may range from 1 to 300 mm. The printed circuit board1 is electrically connected to one pole of the current source which hasnot been illustrated herein, and the counter electrodes 16 to the otherpole of the current source.

Holders 9 for holding a cover 8 of the bath tank 4 which advantageouslytravels together with the supporting frame 17 are mounted in the topregion of the supporting frame 17. As a clearance is created between thesupporting frames 17 to receive the circuit board 1 or remove same therefrom the parts of the cover 8, too, let a clearance be created betweenthem in order to let the circuit board 1 to be lowered into or bewithdrawn from the bath tank 4. The cover 8 serves to prevent, or atleast strongly limit, escape of toxic vapor from the electrolyte fluidduring the electrolytic treatment. In addition, a suction device (notshown) for also evacuating the vapors as the printed circuit board 1 isbeing placed into, or removed from, the tank may also be mounted to thetop region of the bath tank 4.

An alternative implementation of the vertical dip tank is shown in FIG.9. Like reference numerals as in FIG. 1 denote like elements. Here, thebottom mounting boards 27 for the printed circuit board 1 on the side ofthe supporting frame 17 are not supported by the side walls of the tank4 as it is the case in the embodiment shown in FIG. 1. As contrasted tothat implementation, the mounting boards 27 in this embodiment arerather formed like tongs that are pivoted through an axle in a mountingboard 21 which is provided on the side of the tank 4 and is mounted tothe bottom thereof. As a result thereof, the circuit board 1 can besimply clamped between the contact strips 5.

Further details of the contact strips 5 are described with reference toFIG. 2 a. FIG. 2 a is a cross-sectional view of one half of the devicein FIG. 1, taken along the line B-B passing horizontally through one ofthe vertically oriented contact strips 5 and through the circuit board1, as viewed from the top.

In the bottom portion of FIG. 2 a, the vertically hanging printedcircuit board 1 is shown as viewed from the top. In the Figure thecounter electrode 16 is disposed there above, parallel to the printedcircuit board 1. The contact strips 5 serve to electrically contact theprinted circuit board 1 via their border region 24.

FIG. 2 b shows a detail of FIG. 2 a. It shows how the electric currentis supplied to the printed circuit board 1: Current supply conductors 7and contact elements 14 as well as electric cables (not shown)connecting the electroplating current source, which has not beenillustrated herein either and serves to supply current, with the circuitboard 1 serve this purpose. The latter may be implemented as a directcurrent source (e.g. a rectifier) or as a pulse current source. Thecontact element 14 may be formed as a cylindrical pin or as an elongatedbar.

From the current supply conductor 7, the current is run through thecontact holder 13 and a conductive spring element 12 to the electricalcontact element 14. Except for the contact element 14, all of thecurrent supply elements (current supply conductor 7, contact holder 13,conductive spring element 12) are electrically isolated or sealedagainst penetrating electrolyte fluid so that the elements will not getin touch with the electrolyte fluid. A seal 15 is provided for oncontact element 14 for this purpose. In this example, the contactelement 14 is an inexpensive to manufacture annular contact made from achemically stable material such as titanium. The seal 15 is formed by awear resistant, elastic O-ring made from a plastic material that isnested in a groove in the insulating housing of the contact strip 5 ifthe contact element 14 is a cylindrical pin. Such shape is much moreefficient in sealing than any other shapes of the contact element 14 andof the seal 15. If the contact element 14 is formed as a cylindricalpin, an elongated row of such elements 14 is provided for in the contactstrip 5 in order to provide electric contact between the contact strip 5and the circuit board 1 at the entire length of the border 24 of thecircuit board 1.

In order to prevent metal from undesirably depositing onto the contactelement 14, when the printed circuit board 1 is cathodically polarizedfor electrolytic metal plating, the side areas of said contact element14 not abutting the surface of the circuit board 1 can be provided withan electrically non-conducting insulating coating.

As the contacting area of the contact element 14 must in any eventremain electrically conducting, there is a risk that metal deposits onthe contact element 14 when the lateral insulating coating is damagedfor example. The auxiliary electrode 26 allows to dissolve this metal.For this purpose the auxiliary electrode 26 may for example becathodically polarized with respect to the contact element 14 while thecircuit board 1 is being introduced or removed from the tank 4.Accordingly, the contact elements 14 will be anodically polarized. Thisis achieved using electric or electronic switching means (not shown) andthe existing plating current source. A separate rectifier may also beused for this purpose. Possible metal deposits on the contact elements14 are thus removed again. Alternatively, the counter electrodes 16 canalso perform the function of the auxiliary cathode 26 with the provisothat the material used for the counter electrodes 16 is suited forcathodic operation and is not destroyed in the process. As the exposedarea of the contact elements 14 is relatively small, a high currentdensity may be applied for deplating, also using the rectifiers intendedfor the actual treatment, so that complete deplating can be achievedwithout any problem during the process of introducing or removing theprinted circuit boards.

In a special embodiment of the invention, the contact elements 14 mayalso be made of an electrically conductive, elastic material. In thisevent, the seal 15 and the spring element 12 may be absent because theirfunctions, which consist in sealing the electric conduit in theinsulating housing 19, which accommodates the current supply conductor 7and the contact holder 13, against electrolyte fluid and in exerting auniform pressure onto the contact element 14 pressed against the printedcircuit board 1, can be performed by the elastic, conductive contactelement 14 itself. In this event, the contact holder 13 can be firmlyconnected to the current supply conductor 7 so that the connectionexhibits good conducting properties, for example by screwing. If thecontact elements 14 are expected to be subjected to little wear, theelastic contact element 14 may be secured directly to the current supplyconductor 7 so that the contact holder 13 may also be absent.

For electric connection of the electric cables (not shown) to thecurrent supply conductor 7, the latter is led out of the insulatinghousing 19 by at least one end thereof while being provided with afluid-tight seal. The electric connection itself is sealed allover withan elastic plastic material that is chemically stable to the electrolytefluids utilized, or is integrally molded, in order to prevent electriccurrent from flowing between the connection or the current supplyconductor 7 and the counter electrode 16.

The counter electrodes 16 may either be secured separately in the bathtank 4 or be directly mounted on the supporting frame 17 through counterelectrode holders 18. FIG. 2 a shows the latter implementation. In thisalternative, the supporting frame 17 is provided with counter electrodeguides 18.1. The counter electrodes 16 are preferably disposed oppositethe circuit board 1 and parallel thereto. The counter electrode holders18 are not firmly mounted in the slot-shaped guides 18.1 at thesupporting frame 17 but are movably guided therein. As a result thereof,the counter electrodes 16 can be moved by means of suited drives (notshown), for example by means of a motor driven eccentric (with circularup and down or left and right movements), a hydraulic or a compressedair cylinder. The counter electrodes 16 can be moved with a lowfrequency of for example one travel per minute or faster. They need notbe moved constantly during the entire electrolysis procedure. Themovement may also be stopped at times.

In the FIGS. 1, 2 a, 3, 4, 5, the counter electrodes 16 are shown asinsoluble electrodes made for example from expanded titanium metal. Inprinciple, soluble counter electrodes 16 may also be used, though. Inthis event, the counter electrodes 16 are for example implemented as acarrier being insoluble in the electrolyte fluid and receiving the metalpieces employed. Due to the greater weight, the supporting and movingmembers 17, 18, 18.1, 21, 22, 23, 27 must then be provided with agreater supporting force.

In order to maintain metal ion concentration in a plating bath whenusing insoluble anodes (counter electrodes), compounds of a redox couple(e.g. Fe²⁺/Fe³⁺ salts for a copper plating bath) and a replenishingcontainer (not shown) preferably separate to the bath tank 4 and incommunication with the bath tank 4 are provided. The replenishingcontainer contains metal pieces (e.g. copper pieces) to be dissolved bythe chemical action of the oxidized compounds of the redox couple (e.g.Fe³⁺ salt), which oxidized compounds are in turn reduced to the reducedcompounds thereof upon this dissolution reaction. The oxidized compoundsare then recovered by electrolytic oxidation of the reduced compounds atthe insoluble anode in the bath tank 4.

It is further possible to segment the counter electrodes 16 and tosupply them with various voltages for example in order to compensate avoltage drop occurring within the to be treated (base) layer of metal onthe printed circuit board 1 and to achieve the same current densities inall of the printed circuit board regions.

If the work piece 1 is not a flat printed circuit board as it is shownherein, an impression left by the counter electrodes 16 in the form ofcoating thickness differences on the work piece 1 can be selectivelyutilized for certain desired effects (for example electroforming). Inthis event, the moving system for moving the counter electrodes 16 isabsent or the movement is exactly adjusted to the desired effect.Moreover, anode molds that conform to the shape of the work piece 1 maybe used.

To contact the printed circuit board 1 in the border region 24 only, itis assumed that the size of the supporting frame 17 and the position ofthe contact elements 14 conform exactly to the shape and size of theprinted circuit board 1. For particularly uniform current supply, theprinted circuit boards 1 are contacted on all four sides (if the boardsare rectangular). Accordingly, current is fed into the printed circuitboard 1 from all four sides. The only region in which the printedcircuit board 1 is not electrically contacted is the region of theholders 3 to which it is secured.

If the printed circuit board 1 is not conveyed by means of flight barsbut by tongs mounted to conveyor carriages, said printed circuit board 1can uniformly be placed in electric contact through all the side borders24.

In order to prevent the electric field lines from concentrating in theborder region 24 of the printed circuit board 1, shields 38, 39 can bemounted to the supporting frame 17 or to the contact strips 5 (orcontacting frames). Here, the shields 38, 39 are oriented parallel tothe printed circuit board 1. In the embodiment shown in FIG. 2 a, theshield 38 is a remote shield which is disposed between counter electrode16 and the printed circuit board 1 and is located in proximity to thecounter electrode 16. The shield 39, which is termed a proximate shield,is disposed in proximity to the printed circuit board 1. The remoteshield 38 generates a soft shield transition at the printed circuitboard 1, whereas the proximate shield 39 creates a rather sharptransition between the shielded region on the circuit board surface andthe unshielded one. The best results are obtained in combining the twoshields 38, 39. For a softer transition, the shields 38, 39 mayadditionally be provided, in those regions of the shields that areturned toward the center of the printed circuit board 1, with holes ornotches.

Since, in the preferred embodiment shown herein, a printed circuit board1 is being held by the supporting frames 17 contacted on all four sidesby means of the contact strips 5, various measurements may be taken onthe circuit board 1 before and during the treatment of the board 1. Forexample, a comparison measurement of the electrical resistances on theboard 1 between the contact strips 5 in the four border regions 24 ofthe board 1 and a counter electrode 16 can be taken prior to switchingon the electrolysis current, this measurement permitting to readilydetect deviations from reference commands and for example to trigger analarm in the event of unacceptable deviations.

The amount of deposited metal can for example be determined withprecision in the light of the known surface area of the various circuitboards 1 that is operative in the electrolytic treatment and of a chargemeasurement during the electrolysis treatment (ampere-hours count of theconsumed current) and, in the event of deviations from the referencevalue, the metal deposition time may be extended or the current densityincreased for example.

All of the measurements can be acquired and recorded using a connectedcomputer system. Faults may thus be inferred there from at a later stageas well, permitting selective correcting measures to be taken.

The flight bars 2 in vertical lines, move the printed circuit board 1 bymeans of conveyor carriages (not shown) from one processing device(processing station) to the next one. Another advantage of the inventionis that these bars 2 need not be electrically conductive. The sameapplies to the holders 3. Here, the current is run directly to theprinted circuit board 1 through the contact strips 5. Therefore, alight, electrically non-conductive material may be used for the flightbars 2 and holders 3. If the conveyor carriage is provided withcontrolled tongs or grabbers of its own that are capable of taking holdof the work piece 1 at the entry station and of holding them during thetransport, the flight bar 2 may even be absent. The conveyor carriage(not shown herein) for the flight bars 2 may then be provided with areduced carrying capacity compared to conveyor carriages in conventionallines.

As the conveyor carriage is freely movable above the path of travel ofthe printed circuit board 1, additionally provided processing devicesmay be approached in the event deviations from the reference value aremeasured on individual printed circuit boards 1 in order to compensatefor deviations detected by control measurements. If, due to a damage forexample, an increased transition resistance is noticed on one contactstrip 5, the printed circuit board 1 of concern can be subjected to apost-treatment in a special processing station in which at every singleone of the contact strips 5 individual current and voltage values can beset. Accordingly, in this case, the printed circuit board 1 is suppliedwith current through only that border region 24 through the contactstrip 5 of which the failure was measured.

Likewise, the printed circuit board 1 can be subjected to post-treatmentin another bath holding a special electrolyte if for example ameasurement of the brightness of the electrolytically deposited metallayer, which was taken at the end of the treatment, is indicative of adeviation from the reference value. For this purpose, the process forconveying the printed circuit board 1 can be triggered automaticallythrough a suited control system for conveying the printed circuit board1. Once the printed circuit board 1 has been transferred to a repairstation, a special control programme for repairing the failure can berun. Such a programme may for example also include that excess metaldeposited onto the printed circuit board 1 is removed again by reversingthe polarity of the plating current source at the printed circuit board1 of concern (deplating mode). By shielding the supporting frame 17,deplating may be carried out at one printed circuit board 1 while metalplating is performed at another printed circuit board 1.

As it is possible, in printed circuit board manufacturing, to treat onesingle printed circuit board 1 with each supporting frame 17 having thecontact strips 5 (or a contacting frame), appropriate process parameterscan be controlled during manufacturing of this printed circuit board 1by the selective online measurement of current, voltage, charge(ampere-hours), potentials and for example the flow rate of processingfluid on certain sites of the printed circuit board 1 much moreaccurately than with the known devices.

FIG. 3 represents the same view of the device in accordance with theinvention as FIG. 2 a. The reference numerals in this Figure correspondto like numerals in FIG. 2 a and FIG. 2 b. In this Figure, the contactstrips 5, which are shown in a cross-sectional view as view from the topand are secured to the supporting frame 17 in the form of a closedcontacting frame, are complemented by a rear frame cover 20. It has beenfound out that the movement of the electrolyte fluid greatly affects thetreatment result of electrolytic metal plating and electrolytic etching.The rear cover 20 serves to control the flow of the electrolyte fluidand to enhance the flow through the vias in the printed circuit board 1.Accordingly, during the electrolytic metallization of printed circuitboards 1, electrolyte fluid can be supplied to the front side of thecircuit board 1 through tubes 25 by means of a pump (not shown) at forexample a higher pressure than to the rear side of the circuit board 1.The thus obtained pressure drop leads to an enhanced flow through thefine through-plated vias of the circuit board 1. Another possibility ofcontrolling the fluid flow is to lay the feed tubes 25 on either side ofthe cover 20 in the bottom region thereof and to allow the electrolytefluid that has been caused to flow through the supporting frame 17 toexit at the top (or vice versa) through ports in the cover 20 or in thesupporting frame 17. As the space between the circuit board 1 and therear supporting frame cover 20 is relatively small, it is possible toachieve, with moderate pumping capacity, a very high and uniform flowrate over the entire width of the circuit board 1. The mass transfer atthe surface of the circuit board 1 and the suction effect in the viasand blind vias (Venturi effect) are considerably improved and moreuniform.

The embodiment shown in FIG. 3 differs from the embodiment of the devicein FIG. 2 a in that the contact strips 5 are sealed against the outerspace between the covers 20 (only one cover 20 is shown) duringreception of the printed circuit board 1 and closure of the electrolytecompartments. A sealing frame 41, which is secured to one of thecontacting frames 5 and surrounds the entire periphery of theelectrolyte compartment, and a seal 40 embedded in said sealing frame 41serve this purpose.

FIG. 4 shows the same bath tank 4 as FIG. 1. The reference numerals inFIG. 4 corresponds to like numerals in FIG. 1. However, the drive forthe movement of the two supporting frames 17 shown has been changed ascompared to that in FIG. 1. The displacer cylinder 22 and the displacerpiston 23 for each supporting frame 17 have been replaced by cross-rods6 that will perform the function of holding the supporting frame 17 andthe possibly existing additional elements such as the counter electrodes16 and possibly the rear supporting frame covers 20 (not shown herein)and of displacing them. The contact strips 5 are opened and closedthrough a shear mechanism. The drive for the cross-rods 6 has not beenillustrated herein. Eccentric drives, hydraulic cylinders, compressedair cylinders or the like are suited for use as a drive.

FIG. 5 shows the application of contact strips 5 in a horizontalconveyorized line. For increased clarity, the front wall of the tank isremoved, the work piece 1 is shown in a sectional view.

The printed circuit boards 1 are not conveyed through an electrolyticprocessing cell continuously but intermittently. For the production ofthicker layers, a plurality of such cells (electrolysis devices) may bedisposed behind each other in a conveyorized plating line. If theintermittent electrolytic treatment is intended to be combined with acontinuously conveyorized pre- and post-treatment, it is necessary toprovide for a buffer in front of, and if need be, behind theelectrolytic processing cell, said buffer permitting to place thecircuit boards 1 ready for discontinuous operation in due time. In thepresent example, the circuit boards 1 are caused to enter theelectrolytic processing cell from the left, shown by arrow 32. Conveyingrollers 29 serve to convey the circuit boards 1 in this direction. Inorder to prevent the conveying rollers 29 from undesirably shielding theelectric field lines, said rollers are preferably only disposed on theedges of cut 24 (not shown in this Figure, correspond to those inFIG. 1) which laterally extend in the direction of transport 32 betweenthe contacts. At the entry and exit region of the electrolytic cell,additional supporting rolls may be disposed between the contact strips 5that are arranged transversely to the direction of transport 32. As thecircuit boards are entering the electrolytic cell, the supporting frames17 with the contact strips 5 are open, meaning they have been removedfrom the printed circuit board 1 upward, and possibly also downward. Inthis condition, the current is switched off and the electrolyte fluid isin the bottom region of the tank 4. Upon completion of the treatment, aprinted circuit board 1 exits the electrolytic cell through the port 31with the help of the conveying rollers 29 in this position.Simultaneously, another board 1 to be treated is introduced through port30. Once the circuit board 1 has adopted the right position, the drive(not shown) of the conveying rollers 29 is switched off and the top, andpossibly the bottom, supporting frames 17 are moved vertically againstthe horizontal circuit board 1 until the contact elements (not shown) atthe contact strips 5 have established a secure low-impedance electricalconnection to the rectifier (not shown). Then, the moving drive (notshown) for moving the supporting frames 17 is switched off andcirculation pumps (not shown) for the electrolyte fluid are switched on.The electrolyte fluid is thus delivered to the electrolytic cell throughthe tubes 25. As the contact strips 5, together with the supportingframes 17 and the rear supporting frame covers 20, completely enclosethe circuit board 1, the electrolytic cell is filled with electrolytefluid in no time. Sealing rollers 28, which prevent electrolyte fluidresidues from escaping through the entry and exit ports 30, 31 duringthe opening of the supporting frame 17, may additionally be mounted tothe entry 30 and to the exit 31, respectively.

FIGS. 6, 7 and 8 show specific embodiments of the device in accordancewith the invention. In these cases, the supporting frame describedhereto before that opens rearward has been substituted for twosupporting frame parts, said supporting frame parts being formed bydouble contact strips 36 that open in the fashion of tongs (FIG. 8) andeach have contact strips 5 comprised therein (FIGS. 6, 7). The doublecontact strips 36 are retained on a common supporting frame part 37.Three double contact strips 36 hold of and contact one verticallypositioned printed circuit board 1 by the edges of cut 24, both on thebottom and on the sides. At the entry and removal side (side at whichthe printed circuit board 1 is held by the flight bar 2 through theholders 3), there is no double contact strip 36 so that the printedcircuit board 1 can be introduced into, and removed from, theelectrolyte fluid without hindrance.

FIG. 6 shows a detail of such a double contact strip 36 in the sameviewing direction and illustration as in detail A in FIG. 2 b. Tointroduce the printed circuit boards 1 into the electrolytic cell, andto remove them there from, the double contact strips 5 are opened bycausing them to rotate about axle 34 instead of having the supportingframes on either side of the printed circuit board 1 being moved apart.The double contact strips 36 may also be closed again by causing them torotate about the same axle 34 in the opposite rotation direction. Thevarious elements of the device within the insulating housing 19 areidentical to those of FIG. 2 b. The holding arms 35, the axle tube 33and the axle 34 are provided for holding the contact strips 5. The axle34 is secured to a common supporting frame part 37 through elements thathave not been illustrated. Likewise, the drive for this motion ofrotation for opening and closing the contact strips 5 (not shown) can bemounted to said common supporting frame part 37.

FIG. 7 clearly shows how the printed circuit board 1 is introduced andremoved. FIG. 7 shows the double contact strip 36 of FIG. 6 in the opencondition. In this position, the double contact strip 36 is rotatedabout the axis 34 and the contact strips 5 are open in the manner oftongs. The printed circuit board 1 is thus released and is, in thisposition, free to be removed from the device or moved toward the feedregion (see arrow) without hitting something and without beingscratched. For a better understanding, FIG. 8 shows the arrangement ofthe three double contact strips 36 on the three edges of cut 24 of theprinted circuit board 1. The viewing direction illustrated in FIG. 8 isreferred to with “view C” in FIG. 6. One advantage of this embodiment isthat the double contact strips 36 permit to bring counter electrodes 16(as shown in FIGS. 1, 2 a, 3, 4) very close to the circuit board 1. Inorder to move the counter electrodes 16 close to the circuit board 1during the electrolytic treatment, additional moving facilities arerequired. In this case, a rear supporting frame cover 20, such as theone shown in FIG. 3, can be firmly connected to the movable counterelectrode 16.

A simple embodiment, which proved efficient in practice, of a contactingframe comprising four contact strips 5 is shown in FIG. 10 and isillustrated in detail in a sectional view taken along line A-A in FIG.11.

In this embodiment, the contact strips 5 consist of an electricallyconducting, resilient flat material to which current supply conductors 7are screwed, soldered or welded.

Approximately evenly spaced, narrow grooves are milled in the contactstrips 5 so that the inner side of the contact strips 5 is provided withmany lamellae 12 which concurrently perform the function of transmittingthe electric current to the printed circuit board 1 and thus alsoperform the function of the elements referred to with the referencenumerals 13, 14 in FIG. 2 b.

As can be seen from FIG. 11, the lamellae 12 have a bent front edge thatis ground to be plane-parallel to the contact strip 5. As a result, saidfront area can rest evenly on the printed circuit board 1. As is alsoshown in FIG. 11, an insulating coating is furthermore provided, saidcoating enclosing the contact strips 5 and the integrally formedlamellae 12 except for the regions that are slightly ground and areresting on the printed circuit board 1. The electrically conductingcontact area can be formed by slightly grinding the lamellae that areinitially completely coated with the electrically non-conductingcoating. Accordingly, the ground area forms the contact area forelectrically contacting the work piece 1.

FIG. 12 shows yet another preferred embodiment of the device inaccordance with the invention in which a printed circuit board 1, whichis standing vertically in a treatment tank 4, is retained by twocontacting frames that are also standing vertically on either side ofthe work piece 1 and are formed by four contact strips 5 which extendparallel to the sides of the printed circuit board 1. The contactingframes are connected to a supporting frame 17 through holding members,said supporting frame 17 being secured in the bath tank 4 throughholders (not shown herein). The contacting frames can be displacedparallel to each other in the direction of the arrows by means of motiondrives (not shown), with the printed circuit board 1 being removablyclamped or released in the process.

The contacting frames may for example be implemented as shown in FIG.10. To displace the contacting frames parallel to each other, thefacilities shown in FIG. 1 and FIG. 4 may be utilized. In anotherembodiment, the current supply conductors 7 (shown in FIG. 10) on thefour corners of the contacting frames are configured to be holdingplates serving to hold and guide the contacting frames. Bushings (notshown) are provided in the holding plates. Four round guide axes 42,which allow the bushings to be displaced, are provided on the supportingframe. As a result, the contacting frames can be precision guided backand forth in the horizontal direction. Using a motor driven deflectorrod system that has not been illustrated herein, the two contactingframes are caused to move apart (away from the printed circuit board 1)to open and to move toward each other to establish a contact and toclamp the work piece or to disconnect the work piece and release same.

The description given herein above always assumes that the printedcircuit board 1 is to be electrolytically treated on both sides. Ifhowever, but one side is to be treated, one of the two contacting framesand/or supporting frames and all the associated elements may be absent.Alternatively, the contacting frame and/or supporting frame which areomitted may be replaced by a rear cover 20 (FIG. 3) with feed and drainlines for the electrolyte if this is advantageous for the treatment,meaning if for example the electrolyte is intended to flow throughthrough-holes in the printed circuit board 1.

As edges of cut 24 are also customary in the treatment of thin flexibleprinted circuit foils 1 which are not shaped like a board but are ratherutilized in the form of a tape and are conveyed from one roll to theother (reel-to-reel, roll-to-roll), the invention may also be used toprocess such type foils in conveyorized plating lines. In this event,the printed circuit foils 1 are conveyed intermittently instead ofcontinuously.

If electrolytic treatment is not necessary (e.g., in any of theprocessing stations of a treatment line), the current supply devices andthe counter electrodes may be absent. In this event, the other elementsof the treatment device described herein may be provided for:

Referring to FIG. 1 for example, the contact strips 5 and contactingframes may be provided without said elements having the function oftransmitting electric current to the printed circuit boards 1, though.The contact strips 5 and contacting frames may possibly also becompletely absent so that the printed circuit boards 1 are held by thesupporting frames 17 only.

For treating the printed circuit boards 1 chemically (e.g., in any ofthe processing stations of a treatment line), a special version of thesupporting frame 17 may be used referring for example to FIGS. 2 a, 2 b,in which the current carrying elements 7, 12, 13, 14, 26 of thecontacting device are simply omitted. For the rest, the embodiments ofthe device and method for such a chemical treatment do not differ fromthe embodiments for electrolytic treatment according to the presentinvention as described herein. The printed circuit boards 1 may betreated chemically using electroless metal plating and chemical etching.Accordingly, an invention is also considered of major importance for thepresent application in which the current supply devices are not providedfor or are not used in all of the processing stations of a line. Thefeatures of such a device correspond to those described herein above,with the contact strips 5 having however to be replaced here by strips 5the function of which is not to transmit electric current to the printedcircuit boards 1. If necessary, the strips 5 may in this case also betotally absent. In this case, the printed circuit boards 1 can beretained by the supporting frames 17 only.

Herein after, another embodiment will be described, which is alsoconsidered as being of major importance to the invention:

In this device for processing preferably board-shaped work pieces withprocessing fluids, the work piece is clamped between two cassettehalves, said two cassette halves resting on the surfaces of the workpiece so as to be fluid-tight. This makes it possible to introduce theprocessing fluid into the sealed compartments between a respective oneof the cassette halves and a surface of the work piece for treating thesurfaces. As a result, the treatment is considerably facilitated ascompared to conventional ways of proceeding since the work piece needsnot be conveyed to the various treatment baths. Here, the variousprocessing fluids are supplied one after the other to the sealedcompartments and are brought into contact with the surfaces for the timerequired by the respective treatment. After treatment, the fluid isevacuated from the sealed compartments, and a new processing fluid isadmitted. Another advantage is that the work piece may be selectivelycontacted with the flow of fluid since the work piece can be positionedwith greater accuracy in the cassette than this is the case withconventional processing lines.

The device and the method of the further embodiment are morespecifically suited for use in rinsing processes. In case the device isutilized for rinsing processes only, the cassette halves can take holdof the work piece in corresponding rinsing modules of a conventionalprocessing line and can enclose them to form sealed inner compartments.Then, the rinse waters are admitted into the inner compartments andevacuated again after a given time.

If the device is intended to be used for all the processing steps in aprocessing line, the cassette halves may take hold of the work piece atthe beginning of the treatment so that the sealed inner compartments areallowed to form between the respective one of the cassette halves andthe surfaces of the work piece. The various processing fluids fortreating the surfaces are supplied one after the other to the innercompartments and are evacuated after treatment. The cassette holding thework piece can remain stationary during the treatment.

In the cassette, the work piece can be treated both chemically andelectrolytically while being supplied with current. If an electrolytictreatment is desired, the cassettes may be formed in the way mentionedin the description given herein above, meaning it may be provided withcurrent supply facilities that are configured as contact strips providedon opposing side edges of the work piece and are capable of electricallycontacting the (substantially) opposing side edges of the work piece.Accordingly, the cassette may also comprise supporting frames to whichcontact strips may be secured. Frame covers may further be provided,said frame covers forming the individual cassette halves. The contactstrips may seal the inner compartments against the outer space, orseparate sealing strips with corresponding annular seals are provided,said seals being hollow within and being inflated for providing a seal.Thus, in the event that only some single processing steps are to beperformed in the device, said device may comprise the followingfeatures:

-   -   a bath tank which is filled with constantly circulatable        electrolyte fluid,    -   a conveyor system for transporting the work piece into the        electrolytic cassette and out of it or for discontinuously        moving the work piece in a horizontal position through the        electrolytic cassette,    -   supporting elements to which are secured supporting frames with        contact strips and a rear frame cover, the size of the frame        being dimensioned such that the contact strips take hold of the        work piece at the edges of cut only,    -   a moving system for moving the supporting frame with the contact        strips and the rear frame cover toward the work piece and for        pressing them there against prior to electrolytic treatment and        for moving the supporting frame with the contact strips away        from the work piece after electrolytic treatment so as to permit        to remove the work piece from, and to introduce a new work piece        into, the cassette.

In an alternative embodiment, the contact strips may be replaced byother electric current supply conductors such as clamps, or the contactstrips may be provided with lamellae intended to establish electricalcontact (see FIGS. 10, 11). In these cases, the inner compartments ofthe cassette are sealed against the outer space through other means, forexample through supporting frames that fit on the surfaces of the workpiece or through mutually adjacent supporting frames (FIG. 3). Counterelectrodes are of course provided for electrolytic treatment, saidcounter electrodes being located in the sealed inner compartments.

It is understood that the examples and embodiments described herein arefor illustrative purpose only and that various modifications and changesin light thereof as well as combinations of features described in thisapplication will be suggested to persons skilled in the art and are tobe included within the spirit and purview of the described invention andwithin the scope of the appended claims. All publications, patents andpatent applications cited herein are hereby incorporated by reference.

LISTING OF NUMERALS

-   1 work piece, printed circuit board-   2 flight bar (in vertical dip plants only)-   3 work piece holder-   4 bath tank, treatment tank-   5 contact strips-   6 motion drive for supporting frames 17-   7 current supply conductor-   8 movable cover for entry port-   9 holder for cover 20-   10 stationary cover 20-   11 bath level-   12 conducting spring element-   13 spring-loaded contact holder-   14 (exchangeable) contact element-   15 seal-   16 insoluble counter electrode-   17 supporting frame-   18 counter electrode holder-   19 insulating housing for current supply conductor 7-   20 rear supporting frame cover-   21 mounting board located on the tank, supporting element-   22 displacer cylinder-   23 displacer piston-   24 edge of cut, edge of printed circuit board 1-   25 electrolyte feed and drain tubes-   26 auxiliary electrode for deplating-   27 mounting board on the supporting frame-   28 sealing roller-   29 conveying roller-   30 entry port-   31 exit port-   32 direction of transport-   33 axle tube-   34 axle-   35 holding arm-   36 double contact strip-   37 common supporting frame part carrying the double contact strip 36-   38 remote shield-   39 proximate shield-   40 seal-   41 seal frame-   42 guide axis

1. A device for electrolytically treating an at least superficiallyelectrically conducting work piece (1) having substantially opposingside edges (24), said device comprising current supply devices for thework piece, said current supply devices each comprising contact strips(5) for electrically contacting the work piece (1) at the substantiallyopposing side edges (24).
 2. The device according to claim 1, whereinthe contact strips (5) are configured in such a manner that they arecapable of holding the work piece (1).
 3. The device according to claim1, wherein at least two respective contact strips (5) are combined inone contacting frame and two contacting frames are guidedly movabletoward each other or away from each other for opening and closing sothat the work piece (1) can be removably clamped between the contactingframes.
 4. The device according to claim 1, wherein the contact strips(5) are secured to a supporting frame (17).
 5. The device according toclaim 4, wherein the size of the supporting frame (17) is substantiallythe same as the size of the work piece (1).
 6. The device according toclaim 5, wherein the shape of the supporting frame (17) is substantiallythe same as the shape of the work piece (1).
 7. The device according toclaim 4, wherein the work piece (1) is board-shaped and rectangular andthe supporting frames (17) each have four contact strips (5) that areoriented substantially parallel to the side edges of the work piece (1).8. The device according to claim 4, wherein at least two supportingframes (17) are provided for retaining a board-shaped work piece (1),each of them being associated with a respective side of the work piece(1).
 9. The device according to claim 4, wherein the supporting frames(17) are capable of holding the work piece (1) either directly orthrough the contact strips (5).
 10. The device according to claim 4,wherein the supporting frames (17) are supported on supporting points(21) through supporting elements (6,22, 23,27) in a tank (4) serving tohold processing fluid.
 11. The device according to claim 10, wherein thesupporting elements (6,22, 23,27) are configured to be movable so thatthe positions of the supporting frames (17) relative to the supportingpoints (21) in the tank (4) may be varied.
 12. The device according toclaim 10, wherein the supporting elements (6,22, 23,27) are configuredin such a manner that a board-shaped work piece (1) that is fed betweentwo supporting frames (17) and/or contacting frames each associated to arespective side of the work piece (1) can be clampingly held therebetween.
 13. The device according to claim 1, wherein the devicecomprises counter electrodes (16) that are disposed opposite the workpiece (1).
 14. The device according to claim 13, wherein the counterelectrodes (16) are mounted to the supporting frames (17).
 15. Thedevice according to claim 13, wherein the counter electrodes (16) aremovable parallel to the surface of the work piece (1).
 16. The deviceaccording to claim 13, wherein the counter electrodes (16) are disposedsubstantially parallel to the work piece (1) and are movably carried onthe supporting frames (17).
 17. The device according to claim 13,wherein the size of the counter electrodes (16) approximatelycorresponds to the useful area on the work piece (1) that is to beelectrolytically treated.
 18. The device according to claim 1, whereinmeasuring probes are mounted opposite the surfaces of the work piece(1).
 19. The device according to claim 4, wherein frame covers (20) aremounted to the supporting frames (17) and/or contacting frames in such amanner that the covers (20) and the work piece (1) form closedcompartments.
 20. The device according to claim 19, wherein the covers(20) are fluid-tight or almost fluid-tight or wherein they areion-permeable.
 21. The device according to claim 19, wherein the covers(20) are shaped in such a manner that the counter electrodes (16) aredisposed within the closed compartments.
 22. The device according toclaim 19, wherein feed tubes (25) for feeding the processing fluid tothe closed compartments and drain tubes (25) for evacuating said fluidfrom said closed compartments are provided in the covers (20) and/or inthe supporting frames (17).
 23. The device according to claim 4, whereinthe supporting frames (17), the contact strips (5) and counterelectrodes (16) contained in the device are movable together as onecombined unit in such a manner that, during electrolytic treatment, thework piece (1) is held by this unit while the contact strips (5) can bebrought into electrical contact with the work piece (1) and that afterelectrolytic treatment the work piece (1) can be released from said unitand the electric contact be disconnected again.
 24. The device accordingto claim 1, wherein the device is part of a conveyorized plating line orof a dip plant for treating a work piece (1) being an electrical printedcircuit board.
 25. The device according to claim 24, wherein the devicecomprised in the conveyorized plating line further comprises treatmenttanks (4) that are each equipped with entry and exit regions as well asconveying devices (29) for the printed circuit boards (1) and currentsources for the current supply devices (5).
 26. A method forelectrolytically treating an at least superficially electricallyconducting work piece, comprising electrically contacting the work piece(1) at substantially opposing side edges (24) through contact strips (5)serving as current supply devices.
 27. The method according to claim 26,further comprising holding the work piece (1) by means of the contactstrips (5) and/or by means of supporting frames (17) carrying thecontact strips (5).
 28. The method according to claim 26, furthercomprising, for electrolytic treatment, removably clamping the workpiece (1) between the contact strips (5) and/or the supporting frames(17).
 29. The method according to claim 26, further comprising combiningat least two respective contact strips (5) in one contacting frame andguidedly moving two contacting frames toward each other or away fromeach other for opening and closing, respectively, so that the work piece(1) is removably clamped between the contacting frames.
 30. The methodaccording to claim 26, further comprising—providing supporting frames(17) with four supporting frame legs each which are orientedsubstantially parallel to the side edges (24) of the work piece (1)being a rectangular board and/or linking together at least two contactstrips (5) in one contacting frame and—linking together two contactingframes and/or supporting frames (17) through a respective supportingframe leg or through a contact strip (5) in such a manner that the board(1) is removably clamped between the frames and—electrolyticallytreating the work piece (1).
 31. The method according to claim 29,further comprising disposing counter electrodes (16) on the supportingframes (17) in such a manner that they are facing the work piece (1) onone side at least.
 32. The method according to claim 29, furthercomprising disposing frame covers (20) on the supporting frames (17)and/or on the contacting frames in such a manner that the covers (20)and the work piece (1) form closed compartments.
 33. The methodaccording to claim 32, further comprising shaping the covers (20) insuch a manner that the counter electrodes (16) are located within theclosed compartments.
 34. The method according to claim 32, furthercomprising feeding processing fluid to the closed compartments via feedtubes (25) in the covers (20) or evacuating said fluid from said closedcompartments via drain tubes (25) in the covers (20).
 35. The methodaccording to claim 29, further comprising—receiving and taking hold ofthe work piece (1) by the supporting frames (17) and/or by thecontacting frames,—thereafter starting electrolytic treatment bysupplying electric current to the work piece (1) through the currentsupply devices (5),—thereafter disconnecting electric current supplyafter completion of electrolytic treatment and—finally releasing thework piece (1) from the supporting frames (17) and/or contacting frames.36. The method according to claim 35, further comprising, for atreatment in a dip plant having a plurality of treatment tanks(4),—receiving and taking hold of the work piece (1) by the supportingframes (17) and/or by the contacting frames,—immersing the work piece(1) together with the supporting frames (17) and/or contacting framesinto a first processing fluid in a first treatment tank (4),—in theprocessing fluids in the treatment tanks (4), electrolytically treatingthe work piece (1) by having current supply devices (5) supplying thework piece (1) with electric current and—upon completion of thetreatment in the dip plant, releasing the work piece (1) from thesupporting frames (17) and/or contacting frames.
 37. The methodaccording to claim 36, further comprising, after having immersed thework piece (1) into in a first treatment tank (4), consecutivelyimmersing the work piece (1) together with the supporting frames (17)and/or contacting frames into further processing fluids contained infurther treatment tanks (4).
 38. The method according to claim 35,further comprising, for a treatment in a conveyorized platingline,—moving the work piece (1) in a horizontal direction of transportto the supporting frames (17) and/or to the contacting frames of a firsttreatment device in the line,—after having been received by thesupporting frames (17) and/or by the contacting frames of the firsttreatment device in the line, electrolytically treating the work piece(1) and—after having treated the work piece (1) in the first treatmentdevice, releasing the work piece (1) by the supporting frames (17)and/or contacting frames of the treatment device in the line.
 39. Themethod according to claim 38, further comprising, after having treatedthe work piece (1) in the first treatment device in the line,—treatingthe work piece (1) in further treatment devices in the line and,—afterhaving treated the work piece (1) in any respective further treatmentdevice in the line, releasing the work piece (1) by the supportingframes (17) and/or contacting frames of the respective treatment deviceand moving the work piece (1) in the horizontal direction of transportto further treatment devices.
 40. The method according to claim 38,further comprising holding the work piece (1) by the supporting frames(17) and/or contacting frames remain in one place in the conveyorizedplating line during electrolytic treatment.
 41. The method according toclaim 38, further comprising—moving the supporting frames (17) and/orcontacting frames holding the work piece (1) in the horizontal directionof transport from an entry region to an exit region in the conveyorizedplating line and—moving the supporting frames (17) and/or contactingframes back from the exit region to the entry region after release ofthe work piece (1) in order to be capable of receiving a new work piece(1).
 42. The device according to claim 2, wherein at least tworespective contact strips (5) are combined in one contacting frame andtwo contacting frames are guidedly movable toward each other or awayfrom each other for opening and closing so that the work piece (1) canbe removably clamped between the contacting frames.
 43. The deviceaccording to claim 2, wherein the contact strips (5) are secured to asupporting frame (17).
 44. The device according to claim 2, wherein thedevice comprises counter electrodes (16) that are disposed opposite thework piece (1).
 45. The device according to claim 2, wherein measuringprobes are mounted opposite the surfaces of the work piece (1).
 46. Thedevice according to claim 2, wherein the device is part of aconveyorized plating line or of a dip plant for treating a work piece(1) being an electrical printed circuit board.
 47. The method accordingto claim 27, further comprising combining at least two respectivecontact strips (5) in one contacting frame and guidedly moving twocontacting frames toward each other or away from each other for openingand closing, respectively, so that the work piece (1) is removablyclamped between the contacting frames.
 48. The method according to claim28, further comprising combining at least two respective contact strips(5) in one contacting frame and guidedly moving two contacting framestoward each other or away from each other for opening and closing,respectively, so that the work piece (1) is removably clamped betweenthe contacting frames.
 49. The method according to claim 47, furthercomprising, for electrolytic treatment, removably clamping the workpiece (1) between the contact strips (5) and/or the supporting frames(17).
 50. The method according to claim 27, further comprising—providingsupporting frames (17) with four supporting frame legs each which areoriented substantially parallel to the side edges (24) of the work piece(1) being a rectangular board and/or linking together at least twocontact strips (5) in one contacting frame and—linking together twocontacting frames and/or supporting frames (17) through a respectivesupporting frame leg or through a contact strip (5) in such a mannerthat the board (1) is removably clamped between the framesand—electrolytically treating the work piece (1).
 51. The methodaccording to claim 28, further comprising—providing supporting frames(17) with four supporting frame legs each which are orientedsubstantially parallel to the side edges (24) of the work piece (1)being a rectangular board and/or linking together at least two contactstrips (5) in one contacting frame and—linking together two contactingframes and/or supporting frames (17) through a respective supportingframe leg or through a contact strip (5) in such a manner that the board(1) is removably clamped between the frames and—electrolyticallytreating the work piece (1).
 52. The method according to claim 50,further comprising, for electrolytic treatment, removably clamping thework piece (1) between the contact strips (5) and/or the supportingframes (17).